Tidy Cats 24/7 is the go-to unscented clumping clay litter that works reliably in both standard and automatic litter boxes. Smaller jugs frequently dip under $10 at Walmart, and it's one of the most widely available budget litters in the US.
I use the regular kind of Tidy Cats 24/7 performance litter (not the lightweight kind) and it works really well. Haven't had any serious problems with it. I have an LR4 and three cats.
I had a really weird experience with the last container of Tidy Cats I got. I noticed after a week of being in my automatic litter box that it wasn't needing to be emptied or added to which was unusual, because it was just NOT even clumping whatsoever, it was just a disgusting mess of dark, soaking wet, completely loose litter.
Walmart's exclusive clumping clay litter comes in at $8 for a 14-pound jug, the only major brand that consistently stays under $10. Unscented bentonite clay clumps well enough for multi-cat households.
Farm-store pine pellets run about $8 for 40 lbs, an almost unbeatable cost-per-pound that Reddit cat owners rave about. Naturally neutralizes urine odor and produces almost zero dust or tracking.
Tens of thousands of five-star Amazon reviews back this baking-soda-powered clumping litter that seals odors for days. Frequently goes on sale under $10 for smaller bags, making it the best-performing clumping option at this price point.
Grass seed litter is a Reddit-beloved alternative to clay that clumps better than corn-based litters with virtually zero dust. Smaller bags are available under $10, and it's not a food crop so it won't grow mold like tofu or corn litters.